1. Field of the Invention
This invention relates generally to phased array antennas and more particularly to an antenna configuration which ameliorates grating lobes while having wide effective element spacings on the order of one wavelength.
2. Description of Related Art
Phased array antennas are well known and provide excellent electronic beam steering capabilities. However, such antennas require expensive electronics, such as phase shifters, circulators, amplifiers, etc. associated with each radiating element. To reduce manufacturing costs, antenna element support members such as tiles have recently been developed, each incorporating multiple elements. Where identical tiles are utilized, cost savings can result because such tiles can be mass produced. To further reduce antenna cost, it has become desirable to reduce the element count as much as possible while still providing the same desired aperture size; however, when element spacing exceeds one half wavelength in any regular grid of antenna elements, grating lobes appear when the beam is scanned. In general, element count can be reduced by global random thinning or aperiodic element locations, but such approaches do not lend themselves to tiling and hence do not realize the full cost savings potential of mass production.
Accordingly, it is an object of the present invention to provide an improvement in phased array antennas having wide element spacings.
It is yet another object of the invention to provide an antenna which maintains low peak sidelobes at far higher operating frequencies than a conventional translational-periodic phased array antenna having the same element density.
It is still a further object of the invention to provide a phased array antenna which substantially reduces or eliminates grating lobes while having element spacings which exceeds one half wavelength.
It is yet a further object of the invention to provide a tiled phased array antenna which ameliorates grating lobes for effective element spacings on the order of one wavelength.
The foregoing and other objects are achieved by a phased antenna array comprised of an arrangement of like contiguous tiles in the form of a regular polygon having an identical number and relative positioning of antenna elements which by a judicious choice of tile element positions combined with tile rotations result in an irregular or aperiodic array so as to reduce the effective translational period of the array elements which ameliorates grating lobes for elements having an average density of one per square wavelength, i.e., one wavelength spacing. This is achieved, in one aspect of the invention, by randomly orienting a set of square tiles having, for example, four antenna elements located thereon where two of the antenna elements are aligned with a diagonal of the respective tile, and where the other two elements are equi-distantly located on either side of the diagonal. In one tile embodiment, the first two elements are located in the region adjacent one corner of the tile while the other two elements are located in the region adjacent an opposite corner of the tile. In a second tile embodiment, one element of the four antenna elements is located in the region adjacent one corner of the tile along the diagonal while the other three elements are aligned linearly across a diagonal in a region adjacent the opposite corner of the tile.
Further scope of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood, however, that the detailed description and specific embodiments, while disclosing the preferred embodiments of the invention, are provided by way of illustration only inasmuch as various changes and modifications coming within the spirit and scope of the invention will become apparent to those skilled in the art from the detailed description which follows.